Upgrade or remove MSRV for `bdk-cli` project

[notmandatory]

Describe the enhancement

We should update the bdk-cli MSRV to 1.85 with rust edition 2024. We probably don't need a MSRV at all since this is an end binary and not a library, and it's used primarily for testing. But If we want to be safe then using 1.85 will be the Rust version in the next Debian stable release 13 (trixie) which should be released this week.

Use case

Upgrading the MSRV (or doing away with it) will also unblock #206 and other PRs that have dependencies greater than the current MSRV.

Additional context

https://lists.debian.org/debian-devel-announce/2025/07/msg00003.html
https://packages.debian.org/search?keywords=rust